The present invention relates to an improved stabilizer assembly for use in vehicles, especially in passenger vehicles, and more particularly to a novel slidable device interposed between a torsion bar in the assembly and moving parts of a suspension member of a wheel.
Most passenger vehicles make use of the so-called "independent suspension system for wheels" in which both of the wheels behave independently of each other. This is designed with the purposes of restraining rolling of the vehicle and gaining high performance for road holding and straight running. Heretofore, a passenger vehicle, e.g., an automobile, has been provided with a stabilizer assembly of the type in which a U-shaped torsion bar has its central portion twistably mounted on the frame of the automobile and the opposite ends thereof are secured to the lower arms of a suspension system for the wheels. The stabilizer acts in a manner such that, when a pair of right and left wheels differ in level from each other, the car will be prevented from excessive "rolling" or inclination to either side by the torsional resistance produced in the torsion bar. At the same time, stabilizer assemblies are also required to have stronger or more rigid torsion bars in order to meet the requirements of high-speed operation. However, right and left wheels influence each other through the intermediary of the torsion bar in a stabilizer assembly so that a stronger or more rigid torsion bar will result in many disadvantages. One of the disadvantages is that in the case where a wheel passes over a hole in the road during a straight-running operation, a stronger torsion bar would prevent the wheel from completely falling into the hole, producing as a consequence, a poor road-holding characteristic. In this situation, rolling would also be more amplified in the case of a stronger torsion bar rather than in the case where a stabilizer is not utilized. Another disadvantage is that when a wheel passes over a raised location during a straight-running operation, rolling would be more amplified than in the case where a stabilizer is not utilized and the road-holding feature of the other wheel is lowered by the torsional resistance in the torsion bar, also resulting in poor straight-running performance. Accordingly, there is a demand for an improved stabilizer assembly wherein the aforementioned disadvantages are eliminated.
Accordingly, an object of the present invention is to provide an improved stabilizer wherein a slidable braking device is provided for controlling a torsion bar in a manner that it rarely or only slightly acts when a vehicle runs in a straight path but effectively acts when a vehicle turns.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Pursuant to the present invention, an improved stabilizer is provided, said stabilizer having a torsion bar twistably mounted on the frame of a vehicle. The stabilizer assembly includes a slidable braking device provided at least at one end of the torsion bar. The slidable braking device has one portion thereof secured to an end of the torsion bar and the other portion thereof fixed to the lower arm of a suspension system. The two portions are slidable relative to each other, the stroke of which is limited to a length smaller than the maximum twistable amplitude of the end of the torsion bar. Advantageously, the stroke may vary about 10 mm to 20 mm from the neutral position.
In one embodiment of the present invention, the slidable braking means is of a friction-damper type having a cylinder and piston member secured to the end of the torsion bar and the lower arm of a suspension system. The piston is reciprocal along and within the oil-filled cylinder portion, while the oil is flowable through a hole bored in the piston between upper and lower chambers defined by the piston. The piston has a plurality of piston rings fitted in its side circumference, so that a frictional force or resistance acts against any slide movement thereof resulting from the distortion of the torsion bar. The static friction of the slidable braking device is arranged so as to counterbalance the spring-back force produced in a torsion bar subjected to a preselected amount of deformation.
A hydraulic oil damper is also available instead of the abovementioned friction damper as the slidable braking device. The slidable braking device can be used at one end or at both ends of the torsion bar. In the case of each end type, a weight or the like can be added to each end of the torsion bar, and a spring is interposed between the piston and cylinder portions for normally maintaining a neutral position.